It is known to use reciprocating valves, specifically spool valves, as reversing valves for controlling the operating of reciprocating pumps. Such valves are disclosed in conjunction with diaphragm pumps in, for example, U.S. Pat. No. 3, 304,126 and U.S. Pat. No. 4,472,115. In apparatus such as those disclosed in these patents, a spool valve, often under the influence of a pilot valve, is shifted back and forth to reverse the flow of motive fluid from one side of a diaphragm to the other, thus causing the diagram to reciprocate. Such valves are generally provided in enclosed chambers, thus making it impossible to determine the position of the spool valve by observation of the outside of the spool valve housing. Furthermore, conventional spool valves provide no means by which the spool valve can be secured in one position during servicing or maintenance of the pump or pump control system.
It can thus be seen that the need exists for a valve assembly wherein the position of the valve can be easily detected, and wherein the valve can be secured in a stationary position during maintenance or servicing of the pump.